What is the proper method for collecting a respiratory viral panel Polymerase Chain Reaction (PCR) sample?

Proper Collection of Respiratory Viral Panel PCR Samples

The most effective method for collecting a respiratory viral panel PCR sample is using a nasopharyngeal (NP) swab, which should be collected by a healthcare professional using a flocked, synthetic fiber mini-tip swab with plastic or wire shaft. 1

Collection Methods by Specimen Type

Nasopharyngeal (NP) Swab - Gold Standard

• Tilt patient's head back 70° 1
• Insert flexible shaft mini-tip swab through nares parallel to palate (not upwards) until resistance is met or distance equals that from patient's ear to nostril 1
• Gently rub and roll swab, leaving in place for several seconds to absorb secretions 1
• Slowly remove swab while rotating it 1
• Immediately place swab in sterile tube containing viral transport medium 1
• Must be collected by a healthcare professional using flocked, synthetic fiber mini-tip swabs with plastic or wire shafts 1

Oropharyngeal (OP) Swab - Alternative Method

• Insert swab in posterior pharynx and tonsillar areas 1
• Rub swab over posterior pharynx and bilateral tonsillar pillars; avoid tongue, teeth, and gums 1
• Immediately place swab in sterile tube containing transport medium 1
• If collected with NP swab, both can be combined in a single tube to limit use of testing resources 1
• Should be collected using synthetic fiber swabs with plastic shafts 1

Midturbinate (MT) Swab - Alternative Method

• Tilt patient's head back 70° 1
• While gently rotating swab, insert about 2.5 cm (1 inch) through nares parallel to palate until collar/cuff touches outside of nostril 1
• Rotate swab several times against nasal secretions 1
• Leave swab in place for several seconds to absorb secretions 1
• Repeat for both nostrils using same swab 1
• Immediately place in sterile tube containing transport medium 1
• Requires flocked tapered swab with collar/cuff to ensure proper depth of insertion 1

Nasal/Anterior Nares Swab - Alternative Method

• Insert swab about 1 cm (0.5 inch) inside nares 1
• Rotate swab and leave in place for 10-15 seconds 1
• Using same swab, repeat for other nares 1
• Immediately place in sterile tube containing transport medium 1
• Uses flocked, synthetic fiber or foam swabs with plastic shafts 1

Important Considerations

Swab Materials and Handling

• Do not use calcium alginate swabs or swabs with wooden shafts, which may contain substances that interfere with nucleic acid amplification 1
• Rayon swabs may not be compatible with all molecular platforms 1
• Clinical laboratories should confirm compatibility of collection devices during assay validation 1
• Immediately place swabs in viral transport medium after collection 1, 2

Timing of Collection

• Collect specimens as early as possible in the course of illness 3
• Detection rates are significantly higher when samples are collected within 6 days of symptom onset (51%) compared to 7+ days (30%) 3
• For influenza and coronaviruses, viral load correlates with duration of symptoms 3

Comparative Performance of Collection Methods

• NP swabs generally show the lowest cycle threshold values (indicating highest viral concentrations) 4
• For some viruses, OP swabs may be more sensitive than NP swabs (e.g., adenovirus, pandemic influenza A H1N1) 5
• For other viruses, NP specimens are more sensitive (e.g., influenza B, parainfluenza 2 and 3) 5
• Neither NP nor OP specimens are consistently more effective than the other across all respiratory viruses 5

Transport and Storage

• Transport specimens (preferably on ice) within 1-2 hours after collection 1
• Refrigerate specimens if they cannot be processed immediately 2
• Follow specific transport medium requirements as indicated by the testing laboratory 1, 2

Special Situations

Outbreak Investigation

• At the onset of a suspected respiratory viral infection outbreak, collect nasopharyngeal wash or swab samples from several acutely ill patients 1
• Combine throat and nasopharyngeal samples with refrigerated viral transport media in a single tube 1
• Transport to an experienced laboratory for virus isolation and rapid diagnostic testing 1

Self-Collection Considerations

• Self-collection of nasal swabs can be an alternative when healthcare provider collection is not feasible 6
• Self-collected nasal swabs have shown comparable detection rates to staff-collected swabs for respiratory viruses 6
• Proper instruction and supervision improve the quality of self-collected specimens 1, 6

Common Pitfalls to Avoid

• Incorrect swab type: Using calcium alginate swabs or wooden shafts can interfere with PCR testing 1
• Improper technique: Not reaching the proper anatomical site can result in false negatives 1
• Delayed processing: Specimens should be transported promptly to the laboratory 1
• Collection timing: Collecting samples too late in the course of illness reduces detection rates 3
• Inadequate specimen: Insufficient cellular material can lead to false-negative results 1

For optimal detection of respiratory viruses, collecting combined NP and OP specimens would maximize sensitivity across a large number of viruses 5.